The above-cited Flores patent concerns a special wiping fabric which it calls a dusting fabric. A more widely used wiping fabric, as described in U.S. Pat. No. 4,239,828 (Knope et al.), is a nonwoven, porous, tissue-like material made from 80 parts of rayon fibers and 20 parts by weight of polypropylene fibers, both of approximately 1.5 denier and having been fused together to afford integrity to the fabric, e.g., "Novonette" No. H854 of the Kendall Co. The-Knope patent reports that the fabric was cut to shape and attached to the envelope or jacket material by a single pass of a roll having knurled sections of about 3 mm in width which had been preheated to 175.degree. C. The envelope material was a film of a copolymer of 90 parts of vinyl chloride and 10 parts by weight of vinyl acetate containing about 10% carbon particles and having a matte surface. The temperature of the knurl roll was sufficient to fuse the fabric to the vinyl film without observable change in the overall porosity of the fabric.
Although the Knope patent reports cutting the fabric to shape before thus bonding it to the vinyl film, it is believed that almost all diskettes have been made by bonding uncut fabric to uncut vinyl film and then die-cutting the composite to form a jacket blank having a number of openings including a pair of data transfer slots. See U.S. Pat. No. 4,263,634 (Chenoweth et al.), col. 1, lines 28-42 which states: "This resulted in the edges of the fabric being coincident with the edges of the slots and resulted also in fibers from the fabric migrating or extending from the fabric into the slots on disk rotation thus causing unreliable data transfer by the transducers extending through the slots into contact with the disk. These trouble causing fibers in the data transfer slots of the jacket occurred particularly when overused dulled punches were used, resulting in undue fraying of the fabric." The Chenoweth patent answered this problem as follows: "(A) pair of panels of porous dusting fabric are disposed on each of the two inside surfaces of a flexible magnetic disk receiving jacket. These panels are spaced by gaps which are wider than the jacket slots and in which the jacket slots are disposed, and the edges of the fabric panels are thus out of register with the edges of the jacket slots. These edges of the panels are formed by edge sharpened slitter wheels, so that these edges are cut rather than the result of tearing, and so that the dusting fabric edges have a minimum number of frayed and free fibers that might lodge beneath a transducer in data transferring contact with the disk." (col. 1, lines 52-64).
Even though the dusting or wiping fabric of the Chenoweth diskette is out of registry with the edges of the data transfer slots of the jacket, other edges of the fabric coincide with edges of other jacket openings including the central openings and timing holes. Not only do these edges afford the hazard of loose fibers, but some diskette users consider that the sight of loose fibers at any jacket opening is a sign of poor quality. To avoid this, the punch or die must be exceedingly sharp. Usually such a die cannot be resharpened more than three times without going out of specifications.